Conventionally, to meet a requirement for high integration of semiconductor devices, there has been proposed using a three-dimensional integration technology of stacking semiconductor devices three-dimensionally. As a system using this three-dimensional integration technology, there is known a bonding system of bonding substrates such as semiconductor wafers (hereinafter, simply referred to as “wafers”) (see, for example, Patent Document 1).
In this bonding system, after surfaces of a first substrate and a second substrate to be coupled to each other are modified and hydrophilized, the first substrate and the second substrate are bonded to each other by a Van der Waals force and a hydrogen bond (intermolecular force) in a bonding apparatus.
In the aforementioned bonding apparatus, however, an upper holding unit, for example, holds the first substrate by attracting an entire surface of the first substrate at a side of an upper surface which is a non-bonding surface. For this reason, a transfer device configured to transfer the first substrate with respect to the bonding apparatus transfers the first substrate to the upper holding unit while holding a periphery portion of a lower surface side of the first substrate which is a bonding surface.
Patent Document 1: Japanese Patent Laid-open Publication No. 2015-018919
In the aforementioned bonding apparatus, however, since the first substrate is transferred while the bonding surface thereof is held by the transfer device, there is a concern that particles may adhere to the first substrate. In this consideration, the bonding apparatus still has room for improvement in the aspect of suppressing particles.